To answer your orignal question about hydraulic throw out bearings: myself and a friend have tried them twice and not been happy with the results. Short answer is they leak. Both were meticulously installed and checked so it wasn't the way it was done that made them leak. We ended up going back to a stock fork and throw out bearing and using late model Camaro or S-10 bellhousings with the GM slave cylinder and the Wilwood master that was already in place. Never another leak. To top it all off the Overall cost of using the GM slave and standard fork and bearing is less than 1/2 of the aftermarket set up and even cheaper if you already have some of the parts around.
BTW the late model bellhousing only fits the 194 - 292 family inlines and not the 235 jobs.
